Process of tempering or hardening steel.



UNITED STATES PATENT OFFICE.

JOHN B. MOORE, OF LATROBE, PENNSYLVANIA.

PROCESS OF TEMPERING OR HABDENING STEEL.

No Drawing.

To all whom it may concern Be it known that I, JOHN B. MOORE, a citizenof the United States, residing at Latrobe, in the county of Westmorelandand State of Pennsylvania, have invented new and useful Improvements inProcesses of Tempering or Hardening Steel, of which the following is aspecification.

This invention is a process for treat ng steel, to effect the hardeningor tempering thereof, and the object of the invention is to so treat themetal, that scaling or decarbonization thereof, is avoided during theprocess by which the hardening or tempering is accomplished. It is wellknown that when tools, made of high speed steel, are hardened ortempered by the methods now in common practice, scaling ordecarbonization of the metal takes place to a greater or lesser extent,resulting in a corresponding weakening of the metal structure of thetool. This weakening or deterioration of the metal may be prevented bythe following process, to witzg -lhe tool or piece of metal to betempered is cleaned to free it from oil, greases, and the like, and allscale is removed in any preferred manner. Then, while the tool or metalis perfectly cold, it is immersed in water, and while wet afterwithdrawal from the water, it is rolled in powdered boric acid. The toolor metal is then subjected to the desired tempering heat and then cooledin a suitable bath. Or, if desired, the tool or metal, coated with boricacid, applied as vabove stated, may be preheated slowly to a temperatureof about 1200 Fahrenheit, then removed from the furnace at this heat andagain rolled in powdered boric acid, after which it may be brought upquickly to the proper temperature for high speed steel, about 2500Fahrenheit, and finally cooled in a suitable bath.

Under the action of the heat, in the fore going process, the moisture inthe boric acid is driven off, leaving boron trioxid, which is a thickviscid substance that will adhere to the metal, and will remainunchanged to near the melting point of steel. Boric acid and borontrioxid are neutral with regard to steel in that they will not attackeither the metal or the carbon, and the effect of heating the boric acidupon the metal, as above described, is to provide the metal with aprotecting coating which will not Withdraw any of the carbon from thesteel, or attack the metal in any manner, and which will protectSpecification of Letters Patent.

Patented July 11, 1916.

Application filed February 24. 1915. Serial No. 10,263.

the surface of the metal from decarbonization due to the action of air,furnace gases, or other extraneous source. hand, while boric acid andboron trioxid are neutral withrespect to steel, they have great aflinityfor other substances, and it is desirable in carrying out the foregoingprocess, that the tool or metal being tempered, be kept from contactwith the fire brick lining the furnace, or from coming in contact withany object not constructed of iron or steel, To protect the tool ormetal under these conditions, it is preferred to place the same upon asuitable support of neutral material, during the heating operation, soas to prevent the protecting covering from being attacked. Said supportmay be made of any metal, neutral with respect to boric acid or lloorontrioxid, capable of withstanding the ieat.

After the tempered tool or metal has been cooled, the boron trioxid willstill adhere thereto like a glaze, and may be removed in any suitablemanner. For instance, if left exposed to the atmosphere. the borontrioxid will take up moisture and assume the form of a powder which maybe readily brushed off. The boron trioxid may be more quickly removed,however, by soaking the tool or metal in cold water, but great care mustbe taken to insure that the tool or metal is per fectly cold, beforebeing immersed in the water, as otherwise it may crack.

I claim as my invention 1. A process of hardening high speed steel whichconsists in cleaning the metal, wetting the same with water, coveringthe wet surface with boric acid, whereby the water will cause the acidto stick, heating the coated metal to a degree to convert the boric acidinto a glaze covering the surface of the metal, then increasing thetemperature until the metal reaches a white heat, and finally quenching.

2. The process of hardening high speed steel which comprises cleaningthe metal, causing a coating of boric acid to adhere to the cleanedmetal, heating the coated metal to a degree to cause the boric acid toform a glaze covering the surface of the metal, increasing thetemperature until the metal reaches a white heat, and finally quenching.

3. The process of hardening high speed steel which comprises cleaningthe metal, causing a coating of boric acid to adhere to the cleanedmetal, preheating the coated On the other matal tu form a glamm'or thesurface there- In testimony whereof I havv hrrvunto sub uf applymg asecond coatmg of home new], my hand 1n presence of two subscrllnng\vltagram hoatmg to convert the second coatmg nesses.

into a glaze t m'oring the first glaze, continu- JOHN B. MOORE. 5 mg tomcrvaso the temperature untll the W1tnesses:

metal reaches a \vhlte heat, and finally JAs T. HUGHES,

I quenching. IRA B. SIIALLENBERGER.

